This invention relates to improvements in an air cleaner for filtering and cleaning air drawn by suction into an internal combustion engine.
Generally, an air cleaner of the type described includes a casing formed mostly of sheet iron, and the heat generated in the internal combustion engine is such that the casing can maintain its resilience and is not deformed to a degree that gaps are formed in the seals. However, there has in recent years been a tendency to use a synthetic resinous material for forming a casing to reduce the weight. When this is the case, particularly when a thermoplastic synthetic resinous material is used as material for forming a casing of an air cleaner, the casing tends to undergo creep deformation due to the heat generated in the internal combustion engine, with a result that a sealing load applied to the gaskets to hold in place the annular air cleaning filter element is relieved. A reduction in the sealing load would induce wobbling of the filter element within the casing when vibration of the internal combustion engine and a vehicle mounting such engine is transmitted thereto. This would separate the filter element from the gaskets to form gaps through which unfiltered air would be drawn into the internal combustion engine, thereby having harmful effects, such as obturation of the carburetor and wear caused on the cylinders of the combustion chamber, etc.
To obviate the aforesaid disadvantages of the air cleaner casing formed of a synthetic resinous material, proposals have been made to increase the thickness of the casing, or to add ribs thereto. Although these proposals have effect to a certain extent, it has hitherto been impossible to completely avoid a reduction in the sealing load applied to the gasket which is caused by creep deformation of the casing caused by heat. Moreover, the measures taken in accordance with these proposals spoils the advantage offered by the use of a synthetic resinous material because the amount of the synthetic resinous material required increases and the weight of the casing also increases.